Detailed explanation of using Symfony's Crawler component to analyze HTML instances in laravel

This article mainly introduces the use of Symfony's Crawler component to analyze HTML in laravel. Friends in need can refer to it

The full name of Crawler is DomCrawler, which is a component of the Symfony framework. What is outrageous is that DomCrawler does not have Chinese documentation, and Symfony has not translated this part, so development using DomCrawler can only be explored bit by bit. Now I will summarize the experience in the use process.

The first thing is to install

composer require symfony/dom-crawler
composer require symfony/css-selector

css-seelctor is the css selector, some functions will be used when selecting nodes with css

The example used in the manual is

use Symfony\Component\DomCrawler\Crawler;
$html = <<<‘HTML‘
Hello World!
Hello Crawler!
HTML;
$crawler = new Crawler($html);
foreach ($crawler as $domElement)
{
var_dump($domElement->nodeName);
}

The printed result is

string ‘html‘ (length=4)

Because the nodeName of this html code is html, and my English is not good, I thought the program was wrong when I started using it. . .

In the actual use process, if new Crawler ($html) will have garbled code problem, it should be related to the page encoding, so you can use the following method, first initialize the crawler, and then add node

$crawler = new Crawler();
$crawler->addHtmlContent($html);

The second parameter of addHtmlContent is charset, and the default is utf-8.

For other examples, please refer to the official documentation, http://symfony.com/doc/current/components/dom_crawler.html

Record the work and try it out bit by bit. Usage

filterXPath(string $xpath) method, according to the manual, the parameter of this method is $xpath, and p, p and other blocks are often used.

echo $crawler->filterXPath(‘//body/p‘)->text();
echo $crawler->filterXPath(‘//body/p‘)->last()->text();

The output is the text of the first and next p tag block

var_dump($crawler->filterXPath(‘//body‘)->html());

Output the html in the body

foreach ($crawler->filterXPath(‘//body/p‘) as $i => $node) {
$c = new Crawler($node);
echo $c->filter(‘p‘)->text();
}

filterXPath obtains an array of DOMElement blocks, each The DOMElement block can use the new crawler object to continue parsing

$nodeValues =
$crawler->filterXPath(‘//body/p‘)->each(function (Crawler $node, $i) {
return $node->text();
});

crawler provides an each loop and uses closure functions to simplify the code. However, note that this way of writing $nodeValues ​​gets an array, which requires further processing.

Other usage

echo $crawler->filterXPath(‘//body/p‘)->attr(‘class‘);

You can get the value "message" of the class attribute corresponding to the first p tag

$crawler->filterXPath(‘//p[@class="样式"]‘)->filter(‘a‘)->attr(‘href‘);
$crawler->filterXPath(‘//p[@class="样式"]‘)->filter(‘a>img‘)->extract(array(‘alt‘, ‘href‘))

and above They are some methods of obtaining tag attributes.

filter is different from filter to try.

Generally speaking, I feel that DomCrawler is easier to use than simple html dom. Maybe it is because I use it more easily.

The above are just the basic functions of Crawler. For more usage, please refer to the functions in the Crawler part of the symfony manual

http://api.symfony.com/3.2/Symfony/Component/DomCrawler/Crawler .html

The main problem with Crawler is that there are too few examples. There are no usage examples in the function manual, so you can only explore it in actual use. . . .

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